The present invention relates to a device for the electrical actuation of a safety-critical system. In the background art such a device is known from EP 1 447 830 A1. For secure wired coding of three different switching states, this device has two tiers of switches actuable in a coupled manner, by means of which six connecting leads may be switched into three different connection patterns. As the connection patterns associated with various actions and/or states differ in all of the connection pairs of the connecting leads, each connection pattern is already identifiable from a correct connection pair.
Such an electrical device is further known from DE 199 62 556 A1. In this device too, the electrical connection is effected by means of six switching lines, by means of which the three different switching states may be scanned. However, compared to the device known from EP 1 447 830 A1, the '556 device device additionally comprises a configuration with current direction elements, so that for each switching state a unidirectional current flow arises between the terminals.
One drawback is that manufacture and installation of the known devices entails a high technical outlay and is therefore costly. The reasons for this are above all that, firstly, in order to switch the three different connection patterns a total of six switches have to be coupled and actuated. Secondly, in order to connect to the devices to an electronic control unit a total of six electric terminals have to be provided and a total of six electric lines have to be installed. Thirdly, reliable scanning of the connection patterns for the electronic control unit, because of the total of six electric terminals, entails a correspondingly high outlay for circuitry and software. Therefore it would be desirable to provide a simpler electrical activation device.